In computer systems, files generally are stored in a direct access storage subsystem (e.g. containing one or more disk storage devices, of either fixed or removable form), in association with a standard set of attributes (see definition of "attribute" above) describing certain characteristics of the file and its location in storage. Files and associated standard attributes are created by and revisable by application programs. Storage of files and their standard attribute sets is generally managed by the operating system in a linked manner, so that the files and their standard attributes are accessible to the operating system and other applications (applications different from the one which created the file) as if they were a single entity, even though their locations in storage may be different. This type of coordinated handling of files and attributes is referred to hereafter as "conjoint" handling.
In addition to standard attributes, an application program may create or revise extended attributes or EA's which the application associates with the file data. Hitherto, EA's have been so formed by the creating applications that they are effectively inaccessible to the operating system and other applications. More specifically, such EA's have been formed either as discrete files, which are effectively separate from the other file data created or revised by the application and associable with the latter data only by the creating application, or they have been combined with the other file data in a form such that they are effectively distinguishable only to the application which created them. Thus, although storage of all data is managed by the operating system, EA's have remained effectively inaccessible to the operating system and applications other than the creating application.
Thus, for example, when a file has been copied to another medium or directory, by invocation of a suitable command to a prior art operating system, associated EA's either have not been copied at all or they have been transferred with the file data in an indistinguishable form. In either circumstance, EA's associated with copied file data have not been useful to the operating system or another application. This can be a disadvantage to developers of applications inasmuch as it is often desirable to be able to adapt applications to be able to use file data created by other applications, and without access to extended attribute information, such adaptation would be ineffective.
Furthermore, even if access to such EA's could be obtained by other applications (for instance, via linking information placed in the base file by the creating application), it could be unwieldy to rely on such for linkage because of the diversity of language and identifying techniques used by different applications developers. Thus, the developer of an application seeking to link to a given base file would have to know the technique used by the creating application for identifying the associated EA's, and of course that technique could differ among applications made by different companies and/or individuals. Furthermore such "indirect access" to EA's would add additional processing burdens on both the originating and linking applications, as well as the operating system, when compared to the techniques associated with the present invention.
The foregoing "prior art" handling of EA's is also discussed at length in section 3 of the Detailed Description given hereafter.
It is believed that prior to recent introduction of OS/2 Version 1.2, attributes managed by operating systems have been confined to a small standard set such as that described above: i.e. with fixed context of characters and fixed character length location relative to associated file directory entries (generally, serving to conserve storage space). Thus, for example, existing versions of DOS and versions of OS/2 released prior to version 1.2 of that program have been adapted to manage only the standard set of attributes described above. Consequently, these earlier operating systems have not been able to provide conjoint access to EA's, although considering the above analysis it may now be appreciated that such conjoint access could be highly useful.